The present invention relates generally to catalytic steam-hydrocarbon reforming and more specifically to determining changes in the catalytic activity of the reforming catalyst used in catalytic steam-hydrocarbon reformers. The determination of changes may be for decreases in the catalytic activity of the reforming catalyst as well as for increases due to refurbishment events or catalyst replacement.
Steam-hydrocarbon reforming catalysts are subject to numerous types of degradation, including sintering, carbon formation, and sulfur poisoning. Catalyst degradation results in a decline in the catalytic activity, which in turn reduces the efficiency and economic performance of the hydrogen or synthesis gas production facility. It is therefore important to be able to monitor the activity of the reforming catalyst and quantify the extent of reduced catalytic activity so that catalyst regeneration activities can be scheduled and failure of the reformer can be avoided.
Steam-hydrocarbon reforming catalysts may be refurbished in various ways, including replacement, partial replacement, and steaming. It is important to be able to receive an empirical confirmation that catalyst refurbishment activities have resulted in a significant improvement in catalytic activity, thereby allowing for continued operation of the reforming plant before refurbishment activities are repeated again.
In the prior art, a temperature approach to equilibrium has been used as an indicator for reduced activity of reforming catalyst. This approach requires collection of a sample of the reformate from the reformer furnace and offline measurement of the composition of the sample. The outlet temperature is estimated from the equilibrium constant for the water-gas shift reaction and the composition of the reformate at the outlet. The equilibrium temperature is calculated from the equilibrium constant for the steam reforming reaction at the measured composition for the reformate at the outlet. The temperature difference is the temperature approach to equilibrium.
For a fixed reformer operating condition, a small temperature approach to equilibrium (close to zero) means that the catalyst activity is high and that little degradation of the catalyst has occurred. On the other hand, a large temperature approach to equilibrium means that the catalyst activity has decreased and that the catalyst degradation has occurred. Although the temperature approach to equilibrium is widely used as a diagnostic tool for steam-hydrocarbon reformers, it has a major deficiency. In addition to being sensitive to catalyst degradation, the temperature approach to equilibrium also exhibits significant sensitivities to normal variations in furnace operating conditions, such as production rate, steam-to-carbon molar ratio, reformer operating temperature, and reformer operating pressure.
These variables all affect the conventionally calculated temperature approach to equilibrium, even for constant reforming catalyst conditions. The sensitivity of the conventionally calculated temperature approach to equilibrium to process conditions severely limits its utility as a diagnostic tool for catalyst degradation.
Industry desires new and/or improved methods for monitoring the catalytic activity of reforming catalyst for both increased catalytic activity and decreased catalytic activity.
Industry desires methods for monitoring the catalytic activity of reforming catalyst that is sensitive to changes in the catalyst activity but relatively insensitive to normal changes in process operating conditions.
Industry desires methods for monitoring catalytic activity of reforming catalyst using existing process data, and preferably process data which does not require a sample to be collected and analyzed offline.
Industry desires methods for enabling determination of changes in activity of reforming catalyst, in particular, for enabling determination of reduced activity of reforming catalyst, that is sensitive to changes in the catalyst activity but relatively insensitive to normal changes in process operating conditions.